The days of foreign visitors doing endless "border runs" in order to live - and often work - in Thailand are over, the Immigration Police announced yesterday.

The Kingdom will tighten its immigration rules for tourists who exploit visa-free regulations, starting from the end of the month.

The move will affect tens of thousands of visitors from 41 countries who have been allowed to stay in Thailand for up to 30 days without a visa - often for many months or years.

The 41 visa-exempt countries include Australia, the United Kingdom, Canada, France, Germany, Japan and the United States.

Tourists have been able to extend their stay by travelling to neighbouring countries - Cambodia, Malaysia, Laos and Burma - and returning with a further 30-day entry stamp.

But new rules have been issued because an increasing number of tourists have stayed for extended periods - without paying proper amounts of tax. This has also helped them avoid close scrutiny by authorities here and in their homeland.

"We are trying to make it more difficult for bad people to get in," Immigration Police chief Lt General Suwat Thamrongsrisakul said at a press conference yesterday.

"I don't think it's going to hurt good people because they can apply for a tourist visa [in their homeland]," he said.

The move is expected to have a big impact on the foreign community and some sectors such as teaching and diving, plus places where there are many bars run by foreigners, such as Pattaya and Chiang Mai.

From October 1, tourists from the 41 visa-exempt countries may still enter Thailand without visas and stay for up to 30 days, but they will only be able to extend their stay here two times - that is, for a maximum of 90 days.

And tourists who stay for 90 days must leave the Kingdom for at least 90 days before being permitted to re-enter Thailand.

Suwat denied the crackdown was related to the arrest in Bangkok last month of John Mark Karr, the American teacher who was thought to have been involved in the high-profile JonBenet Ramsey murder case. He said there were many reasons that extended back for a long period.

Suwat conceded the move may cause some problems, but said "maybe we have to do something to make it better [later]".

However, if foreigners wanted to work here they should get a work visa, he said.

A source added: "Under the current rules, people from these countries can stay in Thailand for as long as they want. Some even stay here for one year. Many work illegally in Thailand."

Instead of sightseeing, these tourists have taken advantage of the visa exemption by getting married to Thai women "for reasons other than love", and have conducted business here. Many of them have not paid tax.

The immigration move is a hot topic among foreign residents, and comes at a time when many are fearful about possible changes in regard to firms with local nominees.

Hundreds of comments were logged on local Web boards within hours of the Immigration Department press conference. Some said foreigners should abandon Thailand for neighbouring countries, while others predicted it might force school bosses to pay foreign teachers a proper wage or cause a boom in men wanting to marry Thai women.

Most believed the move could cost Thailand a small fortune.

Meanwhile, plans are under way to simplify the process for foreign teachers to work here as the current system requires 13 separate steps, which take many months to complete.

Heads of international schools have been meeting with the Immigration Department to try to simplify the process.

Thailand recently simplified the process for foreigners who want to become permanent residents. The amount of paperwork required has been slashed and the time involved reportedly cut from more than a year to about four months.

Last year Thailand tightened its immigration rules for South Asian tourists, who were allowed to apply for visas on arrival that permitted them to stay for 30 days. Many of them took advantage by travelling to neighbouring countries and returning to get a new visa on arrival at the airport.

Under the new rules, they are allowed to obtain a visa on arrival only twice from neighbouring countries. They are then required to return to their country of origin to obtain an entry visa to Thailand.